1. Field of the Invention
The present invention relates generally to lifting devices, and more particularly, to a portable wheelchair lift device to provide access to stages, platforms, risers and the like for individuals with disabilities.
2. Description of the Background Art
Under the Americans With Disabilities Act of 1990 (the “ADA”), the U.S. government required that public buildings be accessible to the disabled. For persons requiring a wheelchair for mobility, abrupt changes in floor elevation have to be modified to enable access by wheelchair. For new construction, a ramp is typically provided and the pitch or grade on the ramp can be no greater than one inch of rise per foot of horizontal travel and a horizontal landing five feet in length must be provided for every thirty inches of vertical travel. However, a ramp of such length occupies a significant amount of floor space. For older buildings, or even newer building where space is limited, the requirement for a ramp may simply not be practical.
The ADA also permits a vertical lifting device instead of a fixed ramp. Typically, such lifting devices are permanently mounted and include a short ramp for entering a small car which is raised and lowered by a suitable jack mechanism. Under the ADA, such lifting devices must have side walls no less than forty-two inches high and include a grab bar on one side wall. Travel surfaces must be non-skid, and the jack mechanism must be suitably enclosed.
Some available fixed lifting devices include solid side walls, and may omit a gate on one end of the lifting device. Such lifting devices can be uncomfortable to ride if one is claustrophobic or a young child; moreover, having an open end on a lift car is not safe.
Most stages in public buildings are less than about forty-two inches above the floor or ground level. As used herein, the term “stage” refers to an elevated floor, whether or not the elevated floor is actually a stage in a theater or in an auditorium. Thus, lifting devices that can elevate a user to a stage height of 42 inches are generally acceptable, though it would clearly be an advantage to reach heights of 60 inches or more.
Mobile lifting devices for the disabled are known in the prior art, e.g. as described in U.S. Pat. No. 5,105,915 (Gary) which describes a lifting device having a car including fixed sides and short, one-piece ramps at each end. The car is raised and lowered by a pantograph jack including a hydraulic pump driven by an electric motor controlled by switches. The patent also describes several lifting devices of the prior art.
An improved mobile lifting device is disclosed within U.S. Pat. No. 6,182,798 to Brady, et al., and assigned to AGM Container Controls, Inc., the assignee of the present invention. The '798 patent discloses a lift device with gates at both ends of the lift car, transparent walls, a loading ramp, a dock plate, a stage height sensor, and numerous safety features.
Nonetheless, the mobile lifting device disclosed in the aforementioned Brady '798 patent does not solve all problems that have been experienced with mobile lifting devices. For example, even when the lift car is lowered to its lowermost position, it still does not lie close enough to the ground to allow a user of a wheelchair to wheel himself or herself directly into the lift car. The lifting mechanism is housed under the lift car, so the lift car can never be lowered fully to the ground. Instead, a foldable entry ramp must be provided to enable the user to get into the lift car. This entry ramp not only adds weight and material cost to the mobile lifting device, but also poses an inconvenience to both the user and any attendant assisting the user. In addition, the requirement for an entry ramp imposes space limitations on the lift device. For example, there must be enough space between the stage and any nearby walls, or between the stage and the seating area, to accommodate not only the length of the lift car but also the additional length of the deployed entry ramp.
The mobile lift device shown in the Brady '798 patent includes a stage sensor for enabling the lift device to sense when the lift car has reached the elevation of the stage. This stage sensor must be separately disposed on the stage. Moreover, the stage sensor may inadvertently, or maliciously, be moved out of position, resulting in the lift car stopping at the wrong height.
In addition, the mobile lift device shown in the Brady '798 patent has a fixed width, i.e., the overall width of the lift device is at least as wide as the width of the lift car. It often occurs that such mobile lift devices must be transported through doorways; if the doorway is rather wide (i.e., 48″ or greater), then transporting the lift device through the doorway is usually not a problem. However, it is often impractical or impossible to transport such known lift devices through doorways narrower than 48″, such as relatively-narrow 36″ doorways often found in buildings with single doorways like older schools. This explains why the hydraulic jack mechanism used to raise the lift car is disposed directly below the lift car; were the hydraulic jack mechanism moved out around the sides of the lift car, the overall width of the lift device would be increased even more.
The Brady '798 patent discloses a mobile lifting device equipped with retractable wheels for transport. When the lift device is to be transported, the wheels are extended from the base to raise the base off of the ground. When the lift device is in proper position for use, the wheels are retracted, allowing the base to directly engage the ground. The extension and retraction of such wheels is controlled by a crank which must be rotated to raise or lower each of the four wheels. This requires some significant physical effort, as well as significant time. Moreover, the size of such wheels is relatively small (typically 3.5 inches) to allow the wheels to fit under the base. However, such small wheels make it more difficult to transport the lifting device, particularly over soft and/or irregular floor surfaces, including carpeted floors or stadium turf.
In view of the foregoing, it is an object of the present invention to provide a portable lift device suitable for lifting wheelchair-bound users up to the height of stages, platforms, risers and the like in a safe and reliable manner, and comporting with all applicable ADA requirements.
Another object of the present invention is to provide such a lift device capable of lifting users 60 inches or more above the ground while maintaining a relatively low profile when the lift car is lowered to the ground.
Yet another object of the present invention is to provide such a lift device which requires minimal floor space, and which is capable of allowing users to enter the lift car even when the stage is positioned relatively close to a wall, seating area, or other obstacles.
Still another object of the present invention is to provide such a lift device which can be transported through relatively narrow passageways from one site to another while still providing a space within the lift car wide enough to comply with ADA regulations (a clear inner width of at least 36 inches) during actual usage.
A further object of the present invention is to provide such a lift device as a self-contained unit wherein the elevational height of the lift car can be adjusted to proper stage height by the managers/owners of the facility in a repeatable fashion, without relying upon wands, sensors or switches on the stage, while protecting against inadvertent or malicious alteration by unauthorized persons.
A still further object of the present invention is to provide such a lift which can be quickly and easily transported from one site to the next with minimal effort, while accommodating relatively large transport wheels.
Another object of the invention is to provide a lifting device in which the lift car can be safely raised and lowered by a passenger or an attendant.
These and other objects of the present invention will become more apparent to those skilled in the art as the description of the present invention proceeds.